Recent evidence has implicated the expression of growth regulating oncogenes in the genesis of cancer. This proposal is designed to test the general hypothesis that cancer is caused by progressive changes in the structure and/or expression of such oncogenes. The model system selected for study is chronic myelogenous leukemia (CML). This form of leukemia is usually first diagnosed as a preleukemic state with an increase in white count (release from growth regulation) without the presence of undifferentiated cells. Recurrent releases from growth control, sometimes with a small quantity of blast cells, occur. Finally, in blast crisis, an acute leukemia is seen during which an unregulated accumulation of immature cells appears. Activated CML oncogenes from blast crisis cells will be identified and cloned using the standard NIH/3T3 transformation assay. DNA derived from the chronic phase cells of the same patient will also be used in the transformation assay and comparisons of both oncogenes by restriction map and DNA sequence analyses will be made. In addition, identification of activated CML oncogenes will be explored using an alternative method based on the observation that fibroblast cells from persons with premalignant disease are particularly susceptible to transformation. Thus, fibroblast cells from chronic phase CML patients and patients with hereditary cancers with high incidences of unrelated secondary tumors or extreme sensitivity of unaffected tissues to transformation by irradiation will be used as targets for CML DNA transformation studies. Structure and expression of oncogenes will be studied using a modified Berk-Sharp S1 nuclease assay and standard Quick-blot mRNA immobilization. Since the target cell may define the subset of oncogenes which can cause its own transformation, comparisons of oncogene structure and expression in target cells before and after transformation by 1) irradiation or 2) CML DNA will indicate the relative importance of the origin of the transforming DNA and the target cell in identifying sequences relevant to in vivo tumorigenesis. Oncogene structure and expression will also be studied in all patients during the course of their disease. Thus, correlations can be made between the clinical course and the structure and expression of oncogenes in our patients.